McAfee is warning users to be wary of a new piece of "malware" which has affected around half a million computers in just seven days.

The software pretends to be an ordinary media download, such as the recent St Trinian's remake, or a Girls Aloud song, however, once activated the software asks the user to download a codec to play the supposed media file. Once run, a bundle of adware is installed bombarding the user with pop-ups.

McAfee claims the malware is principally being distributed across the eDonkey and LimeWire file-sharing networks, and is the largest outbreak it has witnessed in three years.